1. Field of the Invention
The present invention relates to an illumination optical system that illuminates an illuminated surface using light emitted from a light source. The present invention further relates to an image projector that illuminates an image display element such as a liquid crystal panel provided on an illuminated surface using the illumination optical system and projects light from an image display element onto a projected surface such as a screen.
2. Description of the Related Art
In recent years, there have been developed various image projectors that project light modulated according to image information using an image display element such as a liquid crystal display element onto a screen or the like at a magnified size (see Japanese Patent Application Laid-Open No. H07-181392).
FIG. 16 schematically shows an image projector disclosed in Japanese Patent Application Laid-Open No. H07-181392.
In the image projector shown in FIG. 16, light emitted from a light source 102 is split into a plurality of bundles of light by a fly eye lens 301, and emerging light is converged with respect to the y direction. The light emerging from the fly eye lens 301 is condensed by a second fly eye lens 302.
The light emerging from the second fly eye lens 302 is used to illuminate a liquid crystal panel 109 via a color splitting system 107 and a collimator lens 108.
In the image projector shown in FIG. 16, the lens cells in the peripheral portion of the first fly eye lens 301 each have a center of curvature radius that is decentered toward the center of the first fly eye lens 301. Thus, the width of light emerging from the first lens unit 301 decreases or narrows with respect to the y direction before entering the second fly eye lens 302, and the angle of light incident on the color splitting system 107 also becomes smaller. In this optical system, the angular range of light incident on the surface of a polarized beam splitting film in the color splitting system 107 is also decreased, and therefore good image contrast characteristics are achieved.
In the illumination optical system disclosed in Japanese Patent Application Laid-Open No. H07-181392, light is condensed with respect to the y direction by the first fly eye lens 301, and there is a step (or difference in height) between adjacent lens cells in the first fly eye lens 301 as shown in FIG. 16.
If there are steps between lens cells of a fly eye lens as is the case with that shown in FIG. 16, manufacturing of the fly eye lens by molding is not easy. In addition, illuminating light is partly cut by the step portions, which leads to a decrease in the illumination efficiency.